Sensors which can measure or detect physical characteristics are known. Often it can be useful to combine the outputs of a plurality of sensors. For example, a user may wish to determine something which requires more than one sensor output. For example they may wish to determine the context of an apparatus. The context of an apparatus may be the physical conditions of the apparatus or a user of the apparatus. For example, the context could be the location of the apparatus, such as whether or not the apparatus is inside or outside or it could be a condition of a user, for example whether or not a disease is present.